When did you first learn high-elevation glaciers were dying?When we started our monitoring program in 1978, people typically described the movement of ice fields as slow — you know, glacial. But in the early ’90s during repeated visits to Peru’s Quelccaya glacier, the largest tropical ice cap on Earth, we realized it was in rapid retreat. Although 168 meters thick at the top, it’s now retreating up the mountainside by about 18 inches a day, which means you can almost sit there and watch it lose ground. Mount Kilimanjaro in Tanzania has lost 84 percent of its ice since 1912. As of our 2007 measurements, it was down to 2 square kilometers. And even that measurement is deceptive because it’s not only losing area but depth. In some places, it may only be a half-meter thick.
How unusual is the warming that these glaciers are experiencing? Whether you’re looking at glaciers in the Andes of South America or in the Himalayas, you see a similar trend. The whole atmosphere is warming in the tropics. But the greatest warming is taking place at the highest elevations — on the order of 0.3 degrees C per decade.
From a science perspective, what’s so special about these glaciers?Weather stations are located where people live — in mountain valleys and other lower-elevation regions. They’re not on glaciers where long-lived ice is around to capture and store pollen, pollutants and isotopic anomalies reflecting seasonal temperature variations. Ice masses on the tops of mountains — sticking out in the free atmosphere — have been collecting climate data and storing them, in many cases for very long periods. One ice core from Mount Kilimanjaro contains climate data going back 11,700 years, far longer than any documented history.
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http://www.sciencenews.org/view/generic/id/40411/title/Receding_glaciers_erase_records_of_climate_history
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